The present invention relates to a recording apparatus for line-wise recording information upon a moving photoreceptor.
Apparatus for recording information upon a moving photoreceptor are known comprising a multiplicity of stationary point-like radiation sources that are distributed along a recording head extending transversely of the direction of displacement of a photoreceptor, and that are individually energisable for information-wise exposing the photoreceptor in response to received information signals as the photoreceptor moves past the recording head. The movement of the photoreceptor may occur either continuously or stepwise.
The transfer of the images of the radiation sources onto the photoreceptor can be achieved by means of lens arrangements, fiber optics or fiber pipes, self-focussing fibers or the like. The radiation sources must be sufficiently small in order to achieve an acceptable image resolution and the spacing between the images of the radiation sources transferred to the photoreceptor must be small in order to give the visual impression of an uninterrupted transverse line on the photoreceptor.
It is considered in the art that at least 10 irradiated points per mm are required on the photoreceptor, so that for recording an information line across a standard DIN A4 photoreceptor, which has a width of 216 mm, a recording head comprising at least about 2200 discrete radiation sources in the form of LED's (light-emitting diodes) is required. A plurality of LED's can be formed as an array on a monolithic semi-conductor chip. By line-wise assembling a plurality of chips, a recording head having a length of 216 mm can be obtained.
It is usual for the recording head to comprise two parallel staggered rows of the radiation sources. In comparison with the use of a single row of radiation sources the spacing between adjacent sources of a row can in those circumstances be doubled while achieving the same image resolution. The illumination of the sources forming the more downstream row, reckoning in the direction of motion of the photoreceptor must be delayed relative to the illumination of the sources of the other row in order that the projected images of the different rows of sources shall be on a common transverse line across the photoreceptor.
Apparatus wherein such a delay occurs are disclosed e.g. in GB Application No. 2,042,746 A of Savin Corporation relating to a multiple variable light source photographic printer, and in EUR Application No. 82 201 314.9 of Agfa-Gevaert N. V. relating to a recording apparatus.
In such previously proposed apparatus the delay function is achieved by means of an integrated delay circuit which is wired to integrated driver circuits for the row of LED's whose energisation responsive to data-bit signals pertaining to a given information line has to be delayed relative to the energisation of the other row of LED's. The production of the necessary conductor wire connections is costly and the production complexity and production costs of the apparatus are further increased if serially connected memories and associated switch means for stepwise advancing signals through the memories are introduced for extending the delay period to more than a single information line period.